Method and apparatus for generating impulses



Nov. 26, 1946.

H. H. B'RAUER ET AL 2,411,648

METHOD AND APPARATUS FOR GENERATING IMPULSES Filed April 21, 1944 2Sheets-Sheet l PULSE PULSE SQUARE WAVE PULSE GENERATOR COUNTER COUNTERGENERATOR NUMBER (sue 'Ml/L YIPLE (sue Ml/L r/Pu- (TRIGGERID 5r COU NTER 0F GINERAYTUR UFPUlSfs/RM Pl/LSIJ' FROM PUL E T (dd/V727? 6)(nu/v70? 7) v I25456'I89l0 SPEED PULSE POWER B MIXER EQJ Q AMPLlFIERAMPLITUDE CONTROL OUTPUT 43 OSCILLOSCOPE HTTORA/EY 2 Sheets-Sheet 2 KEYS N6 K EYS INVENTORS ROBERT W KA/[EEL HOW/7RD h. BRHl/[R INTERLOCKINGINTERLOCKI HT OR/VEY H. H. BRAUVER ET AL.

Filed April 21, 1944 -H-o OUTPUT METHOD AND APPARATUS FOR GENERATINGIMPULSES Nov. 26, 1946.

. generatin pulse to no pulse and 1 amplitude-thereof can be controlledexactly.

I annals I 3 METHOD AND APPARATUS ron GENERATING IMPULSES New YorkApplication April 21,

7.0mm. (or. 117-480) 1944., Serial No. 532,170

This invention relates to a method of generating I impulses .and impulsegenerating arrange-' vments for 'use in connection with automatictelephone systems and the like;

In automatic telephone systems, it is commonly the practice to employ aso-called dial impulse sender to generate code impulses corresponding tothe several digits of the wanted partys line.

, In its commonest form, this dial impulse sender includes a pair ofcontact springs connected in series with the signaling circuit. thesecontact springs being periodically opened under the action of aninterrupter arranged tobe operateda desired number of times determinedby the subg number counterv or metering circuit suitable for scribersmanipulation of a finger hold dial. Such an impulse dial sender includesa mechanical governor, intended to control the regularity of operationof the interrupter so that the, mentioned contact springs, areperiodically actuated with a. uniform interval between impulses. It willbe understood that if a dial impulse sender deviates materially from apredetermined interval,-faulty operation of the switching equipment willtake place. For example, if the mentioned contacts ar interrupted toofrequently, as in the case of a so-called fast dial, the switchingequipment controlled thereby will hav insuiiicient time in which tooperate in accordance with the impulses, and consequently an incorrectoperation of the switching means will take place. On the other hand, ifthe contacts are interrupt d too infrequently, as in the case of aso-called "slow dial, slow-releasing relays associated with saidswitching means will fail to be held operated during the long periodbetween pulses and consequently the switching means will be released.Therefore, it is importantin the original testing, as well as in therepairing ofsuch dial impulse senders, to have a so-called standardimpulse generating device or impulse simulator against which thementioned dial impulse senders can be compared for accuracy ofoperation.

In addition, in the testing of a telephone system, it is frequentlydesirable to employ an impulse sender wherein theperiodicity of thepulses can be varied at will, and wherein the ratio'of the time of pulseto no pulse can be controlled as .desired.

In accordance with the main feature of the present invention,'there isprovided,.for satisfying th mentioned requirements, a method of pulses,in which method the ratio of the speed or frequency of pulsing as wellas the number of pulses and the Another feature of the invention relatesto the-use of thermionic means for; generating pulses of exactpredetermined wave form and periodicity. 1

Otherfeatures and advantages of the invention will appear fromthedetailed description and claims when taken with the drawings inwhich:Fig. 1 is a block diagramrepresenting the I equipment which can beutilized in practicing the invention. V

Fig. 2 illustrates thenature of the generated impulses as observed inthe cathode ray oscilloscope, as enlarged in Fig. 2a;

.Fig. 3 is a, diagrammatic showing of a pulse mined range,.such, forexample, as a range from 600 cycles to 2300. cycles. This generator maybe a standard beat frequency oscillator, the output of which is providedwith a network including a capacitor and a resistor, for the purpose ofdiiierentiating the waves in order to providesharp peaks forcalibrating. The output of the generator is coupled to and suppliespulses to a ten-to-one I. pulse counter 15. This pulse counter may be ofany well-known form, such,

for example, as that shown on page 57 of the RCA Review for July 1940.This pulse counter derives square wave pulses ,of 6 the. frequency ofthosedeveloped by the generator 5 and supplies these pulses to a secondten-to-one, pulse counter 1 of like construction, to which it iscoupled. The second c'x unterv 1 thus, develops triggering pulses of oneone-hundredth the'frequency of those delivered by; the oscillationgenerator 5, and is coupled to, a; square wave generator, 8 of thetrigger type which develops square waves of a frequency determined bythe triggering pulses. This square wave generator, which has provisionsfor changing, at will, the width of its square wave pulses, may be ofthe arrangement shown on page 1'76. of the text book entitledUltra-High-Frequen'cy Techniques}? by Brainerd, Koehler, ReichandWoodruff, tenth printing. v

Thesquare wave, so generatedby thev generator 8, is delivered to a pulsenumber counter 9 (to be described in connection with Fig. 3)

pulses per second and having a variable width (timing) and amplitude.

The present arrangement also includes means for visually indicating theduration, amplitude and character of the impulses delivered by the poweramplifier. This last-named means comprises a mixer 42 of the vacuum tubetype in which signals from the generator 5, th counter 6 and the squarewave generator 8 are mixed and the mixed signals from this mixer aredelivered to a cathode ray oscilloscope 43 which may be similar inarrangement to that shown on page 225 of th text bookUltra-High-Frequency-Techniques, referred to above. The mixed signalsdelivered by the mixer to the oscilloscope will cause the screen of thisdevice to visually indicate the character of the output pulse which willappear as illustrated in Fig. 2. This'visual indication will include theoutput frequency pulses or the square waves A corresponding to th dialimpulses being simulated,

upon which there will be superimposed impulses C from the generator 5and calibrating impulses B from the first counter 6. By counting thenumber of calibrating pulses appearing on the output pulse, thepercentage of pulse to no pulse can be determined quickly and easily.The normal sweep will allow the tens and the approximate units to bedetermined. By expanding this sweep, as shown in Fig. 2a, it will bepossible to determine the number of units and the fraction of the unitsto be estimated.

The pulse number counter generally designated 9 in Fig; 1, may embodythe specific circuit arrangement shown in Fig. 3. In this arrangementthe square wave from the generator 8 is supplied to the input circuit ofa vacuum tube, such as a pentode in which does not pass the square waveuntil it is conditioned to do so in a manner to be described. When thusconditioned, vacuum tube In acts as an amplifier and allows theresultant of the square waves to be communicated to the power amplifier40 and counter circuit.

Vacuum tube I is under the control of means including a counter networkand a blocking oscillator cooperating with manually selected digit keys(to be described) which means discontinues the passage of square wavepulses through vacuum tube In when a number of square pulses,corresponding to the selected digit key, have been communicated. Thesquare wave supplied to the pentode ll] is difierentiated by the lowtime constant combination of a condenser II and resistor I2 and is fedto the grid l3 of the vacuum tube |4 during such time as th manualswitch I5 is momentarily opened. The vacuum tube I4 is biased to cut offso that positive polarity pulses only can pass therethrough and beamplified. I

A triode [6 of the gas or thyratron type, is resistance-coupled to theoutput of vacuum tube l4. Triode l6 conducts whenever a pulse greater inamplitude than the normal negative bias is present at its grid When thetriode I6 conducts, the voltage across the resistor I8 is approximatelyequal to the difference between the 4 plate voltage on plate l3 and thevoltage drop across the triode. It. This sudden high voltage at thecathode of the gas triode is used for two purposes. The first is toraise the voltage at the grid 2|a of a second gas type triode 2| to avalue at which this triode will conduct when a positive puls ofsuflicient amplitude is applied to grid 2|a. The circuit in thiscondition will be referred to as being "primed. The other use of thehigh cathode voltage of triode I6 is to raise the voltage on the screengrid 22a of vacuum tube l0 to a value where the tube III will act as anamplifier and allow th original square wave to be supplied to thecounter network and the power amplifier 40.

The counter network consists essentially of two condensers 23 and 24, aswell as two diodes and 26, and a blocking oscillator 21, condenser 23being appreciably lower in capacitance than condenser 24. The positivevoltage present at the anode of pentode l0, due to the normalnon-conducting condition of this tube will have charged the twocondensers 23 and 24 through the diodes to voltages inverselyproportional to their capacitances. When the voltag on screen 2211 ofpentode I0 is increased by the gas triode l5, pentode Ill conductsduring the positive portion of the square wave, and this will cause theanode 30 to approach zero potential. Condenser 23 will discharge throughthe diode 25 but condenser 24 will hold its initial charge. The negativeportion of the input wave will cut oil the grid of pentode I0, causingthe voltage on anode 30 to return to that of the anode supply connectedthereto. This again charges the two condensers 23 and 24, therebyaccumulating an additional charge on condenser 24 every tim the cycle isrepeated.

From the foregoing, it should be understood that each cycle of the inputwave will produce an additional charge on the condenser 24, during theperiod that the screen of pentode I0 is positive, due to the action ofthe gas triode Ii.

The grid 29 of the blocking oscillator tube 21 is connected to thecondenser 24 so that when the voltage resulting from the charge beingaccumulated on condenser 24 exceeds the positive bias present on thecathode 3|, the tube 21 will conduct, thereby producing a strong pulsein its anode circuit. The grid 29 of the oscillator 21 conducts at thispoint in the cycle, discharging condenser 24 and restoring the counterto its initial condition. Th number of pulses required to fire theblocking oscillator can be controlled by the bias on the cathode bymeans of the multiunit resistor or bleeder 32 and the selectivelyoperated interlocking keys 5| to 59 and 50. This con struction of theinterlocking keys insures that only one key can be closed at any giventime. It will be noted that these keys allow a selection of positivevoltage to be applied to the cathode 3| of the oscillator 21 byconnecting to various points along the multi-unit resistor or bleeder.Consequently, by operating any given one of the switch contacts from 50to 5| a corresponding number of pulses from one to ten can be delivered.

The pulse generated in the anode circuit of the blocking oscillator 21is fed to the grid 2|a of the second gas triode 2|, which has beenpreviously primed. This triode conducts and raises the cathode voltageacross resistor 35 to the potential B minus the drop in tube 2|,

which raises the voltage at the negative terminal of condenser 36. Thepositive terminal of the condenser 36 is now substantially twice Bvoltage,

which'isenough to cut oil! triode l6 and restore the cathode to a lowvoltage. This causes the screen in of the first amplifier tube III todrop in potential, thereby causing this tube to cut oil! and-shut of!the square wave from the output of the counter. The circuit is nowrestored to its original state since condenser 24 is discharged andtube. It is non-conducting, although tube II is still conducting. Thenext pulse from tube l6 "primes tubeZl as before but also causes it tobe cut oil! as a result of the operation of the condenser 36. Condenser36 acts in the same manner as described above where triode 2| cuts ofltriode IS.

The pulse number counter of Fig, 3 may be somewhat simplified as shownin Fig. 4 wherein corresponding parts in both diagrams are designated bythe same numerals. In the arrangement of Fig. 4, the condenser ll isconnected to taken not in a limiting sense but merely as illustrative ofthe invention since there can be various modifications in thesecircuits, within the scope of appended claims without departing from thepresent invention.

What we claim is:

1. Apparatus for simulating dial impulses and the like which comprisesmeans for generating square waves, means for diflerentiating said squarewaves into pulses of positive and negative polarity, means for utilizingthe differentiated pulses of one polarity to cause the communication ofsquare wave pulses to a utilization point, means for selectivelyestablishing one of several possible conditions, each differentcondition being indicative of a different fixed number of pulses desiredin a given group, means for accumulating a component corresponding toeach square wave communicated until the total of said components bears apredetermined relation to said selected condition, and means forterminating the communication of said square waves in response to thefulfillment of said predetermined relation whereby said group comprisesa desired number of impulses.

2. Apparatus for simulating dial impulses and the like which comprisesmeans for electronically generating square waves, means fordifferentiatin'g said square waves into pulses of positive and negativepolarity, means for utilizing the positive pulses to cause theelectronic communication of square wave pulses to a utilization point,means for selectively establishing one of several possible conditions,each diflerentcondition being indicative of a diflferent fixed number ofpulses desired in a given group, means for accumulating a componentcorresponding to each square wave communicated until the total of saidcomponents bears a predetermined relation to said selected condition,and means for electronically terminate in: the communication of saidsquare waves in response to the fulfilment of said predeterminedrelation whereby said group comprises a desired number of impulses. I I

3. Apparatus for producing and visually observing the nature ofrecurring impulses of predetermined character which comprises means forgenerating primary pulses at a frequency sub- "stantially greater thanthat of the desired impulses, means for deriving therefrom a submultiplenumber of secondary pulses, means for utilizing said derived pulses totrigger a source of impulses of predetermined form and amplitude, meansfor setting up a condition indicative of a desired number of-impulses in.a group, means for terminating the communication of said impulses tosaid utilization point inresponse to the fulfilment of said condition,and means for simultaneously developing a visible indication of thenature of said primary pulses and of said secondary pulsesas well as oi!said communicated impulses.

4. In an impulse generating system, a continuously operating pulsegenerator, a wave generator triggered by pulses from said pulsegeneratorto deliver impulses, and an impulse number counter coupled to said wavegenerator and selectively operated to deliver a predetermined number ofimpulses.

5. In an impulse generating system, a generator of primary pulsesgreater in number for a given unit of time than the number of impulseseventually desired, a pulse counter for developing from said primarypulses a'sub-multiple number of secondary pulses for the given unit oftime, a square wave generator coupled to said counter and triggeredthereby to develop square wave impulses, and an impulse counter coupledto said wave generator and selectively operated to deliver apredetermined number of said impulses.

6. In an impulse generating system, a generator of primary pulsesgreater in number per given unit of time-than the number of impulseseventuallyv desired, a primary pulse counter for developing from saidprimary pulses a sub-multiple number of secondary pulses per the givenunit of time, a secondary pulse counter for developing from saidsecondary pulses a further sub-multiple number of pulses per the givenunit of time, a square wave generator coupled to said secondary pulsecounter and triggered by pulses therefrom to develop impulses, and animpulse number counter coupled to said wave generator and selectivelyoperated to deliver a predetermined number of said impulses.

'7. In an impulse generating system, a generator of pulses greater innumberper given unit of time. than the number of impulses eventuallydesired, a primary pulse counter for-developing from said primary pulsesa sub-multiple number of secondary pulses per the given unit of time, asecondary pulse counter for developing from said secondary pulses afurther sub-multiple number of pulsesper the given unit of time, asquare wave generator coupled to said secondary counter and triggered bypulses therefrom" to develop square wave impulses, an impulse numbercounter coupled to said wave generator and selectively operunit andcontrolled thereby to display the resultant of said primary andsecondary pulses as well as said square wave impulses.

HOWARD H. BRAUER. ROBERT W. KNEBEL.

